Singular Time-Dependent Photoconductivity Response of MAPbI3 Samples Deposited by Vacuum Processing on Different Substrates

Organo-inorganic halide perovskites continue to generate enormous interest for their potential use in various optoelectronic devices. Among the different fabrication methods, vacuum thermal deposition allows uniform films over large areas, providing good material quality without using organic solvents. However, the influence of the substrate on the properties of the material deposited by vacuum processing is a point that deserves further investigation. Herein, time-dependent photoconductivity measurements are used to investigate the dynamics of charge carriers under illumination in planar films of CH3NH3PbI3. The samples are deposited by thermal sublimation on different substrates: PbI2, TaTm, C-60, and glass. Experimentally, it is shown that the substrate has a profound effect on perovskite behavior and that photoconductivity is sensitive enough to probe these behaviors. Furthermore, a model based on Shockley-Read-Hall statistics is proposed, explaining the different photoconductivity responses by changing only the relative values of the different capture coefficients and the position of the Fermi level. It is argued that the substrate changes the stoichiometry of the evaporated material, affecting the transient photoconductivity response.

Automated summary

This study characterized the film of CH3NH3PbI3 deposited by thermal sublimation on different substrates using time-dependent photoconductivity measurements. The experimental results showed that the substrate had a significant effect on the behavior of the perovskite, and the photoconductivity was sensitive enough to probe these effects. Furthermore, a theoretical explanation based on the Shockley-Read-Hall statistics model was proposed, which explained the different photoconductivity responses by changing the relative values of the capture coefficients and the position of the Fermi level. It was suggested that the substrate changed the stoichiometry of the evaporated material, affecting the transient photoconductivity response.